Control arrangements for escalators typically include devices such as switches, sensors and/or other detectors that are actuated when abnormal or unsafe conditions occur. A signal generated by a detector is then detected by logic circuits or software in the main controller that stop the escalator by de-energizing the main contactors (UP or DOWN) and releasing the brake.
The safety detectors (switches, sensors, etc.) have traditionally been arranged in a series circuit (safety chain), such that actuation of any detector in the chain de-energizes the main contactors (UP/DOWN) and stops the escalator. Safety codes also typically require that some safety detectors be of a manual reset type, requiring physical intervention of a qualified person before a starting key switch is operated.
Safety detectors are typically wired to various junction boxes located in an escalator wellway. The junction boxes are connected to the main controller using a number of conductors bundled in cables.
See, for example, FIG. 5, and also U.S. Pat. No. 5,186,300, Starting Circuit and Method for Escalators and Moving Walks, Feb. 16, 1993, by Zaharia. In these typical arrangements, the present inventor believes that many of the safety detectors have dedicated wiring extending from the detectors substantially to the escalator controller. For the past several years, the escalator industry has experienced many changes because of safety enhancements as well as customer demands for added features. These changes have led to a significant increase in the number of conductors, junction boxes, terminal blocks and other wiring devices. Thus, the cost of labor and materials associated with escalator wiring has increased significantly.
When diagnostic devices are used, the number of connections increases dramatically; which often adds even more to the overall cost of manufacturing the escalator.
Therefore, the cost of making an escalator increases proportionally to the number of safety devices and optional features because of the wiring of these devices and features to the escalator controller.